my 66 coupe, 351W has a tapping sound that we can't seem to cure? like said its like a fast sewing machine sound and to cure it we've redone the cam/lifters/roller tip rockers and adjusted the valves several times? it's a comp cam (hydraulic), trick flow roller rockers 1.6, alum heads, edelbrock intake, and still the tapping. it's not as bad while cold and gets more pronounced the hotter it get? and added the tall valve covers as to give the rockers the room to move. any ideas??? tks a lot